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52mm TB Vs 58mm?

Anyone have real world experience or data (seat of the pants is fine) when upgrading from a 52 to a 58mm Throttle Body? If I'm gonna do it, now is the time when the head is off and the driveway is already covered in metal slivers It's for the 8V motor in my 86S, not full race but fully ported head(stock sized valves), TU Header, GT 30, decent FMIC(for an Omni lol)

Re: 52mm TB Vs 58mm?

I put a 52mm on my custom plenum 2 piece 2.5 in the driveway once vs the ported 58mm I was running. The car seemed to rev up just a hair quicker with the 58 of course but not too noticeable. I didn't get a chance to play with it on the street vs the 58 as I had to wait to seal off the AIS passage on it then winter came and I bought another car and off things went on a tangent.

I guess if you make the manifold for a 58mm TB you can always run a 52 if you like it better vs the other way around.

Re: 52mm TB Vs 58mm?

went from slightly ported 1 piece with 52 to highly ported two piece and 58mm.

Drives the same to me.
It feels a little softer out of boost.
much stronger once boost is going.

I think it was more of a change in the runner shape and size and length on the two piece. than going to 58mm.
58mm drives great. good response.. its not the 'light switch" everyone says.
58MM TB with the throttle blade blocking the air flow. flows about the same surface area as a 52mm pure opening.

Re: 52mm TB Vs 58mm?

I'm using a 75mm TB on my 2.4. It's "way too big" according to some people, but really works fine. When we made the little adapter to put a Chrysler-style cam on the Ford throttle body, we moved it out from the axle centerline a little bit so it would "slow" the opening in relation to pedal movement.
Chrysler did something similar with the MTX vs ATX throttle bodies on 1st Gen Neons. The throttle cam on the MTX TB was a little slower reduce jerkiness, and faster on the ATX cars for better response.

Re: 52mm TB Vs 58mm?

Originally Posted by GLHNSLHT2

I put a 52mm on my custom plenum 2 piece 2.5 in the driveway once vs the ported 58mm I was running. The car seemed to rev up just a hair quicker with the 58 of course but not too noticeable. I didn't get a chance to play with it on the street vs the 58 as I had to wait to seal off the AIS passage on it then winter came and I bought another car and off things went on a tangent.

I guess if you make the manifold for a 58mm TB you can always run a 52 if you like it better vs the other way around.

I like this idea, I'll just cut it for 58 but start with the 52. Then with no other changes swap to the 58 to see if there is an improvement

Ok, back to the porting station where Ive spent over 20 hours in the last couple weeks

Re: 52mm TB Vs 58mm?

I like the idea of running a back to back test. I have both and ran both at a few different times and found the 58 to be better off boost and all around more. The only downside I found was the lack of a ported vacuum source for the vapour canister. My intake was a heavily modded 1 piece

Re: 52mm TB Vs 58mm?

Picked up the mani from the welder today, my old neighbor with the 8 second Fiat welds sh!t for me.(search you tube for 'fast Fiat crash' I shot that vid Gonna make some slivers tomorrow before the game party that almost no one seems to care about the outcome of

Re: 52mm TB Vs 58mm?

Did you have the lower welded up so you can port the pinch point of the bolts in the runners? It makes sense to me that you would really improve the quality of flow with the neck welded up and then shaped. I know you've done that before, so you must find it to be valuable. How much of a difference do you notice when you do that?

Re: 52mm TB Vs 58mm?

It's gotta run by this Friday and I didn't have access to a bead blaster. Lowers are to contaminated with oil to TIG fill them. About 80% of the bolt humps can be taken outta the lowers without welding. Ive never done a 'neck only' mod with no other changes. So this will be the first B2B comparo. That is of course 52 vs 58 with the weld md.I did a 3.8l neck mod last time instead of just fill welding but Woody ripped the tires after that mod.

Re: 52mm TB Vs 58mm?

The 52 felt more responsive at lower rpm on my tiii. The 58 feels more responsive above 4k than the 52 did. No changes were made to either and I did not think to look for any differences in the cam shape.

Before I got the cam timing worked out, the 58 felt very sluggish which I incorrectly attributed to its size.

“If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford

Re: 52mm TB Vs 58mm?

Yeah, T III's and their cams ... Years ago when I got adj gears for the Rampage RT I checked the centerline of the stock gears, intake was 8 degrees off and exhaust was 6 degrees off on factory gears! With the new gears set up exact, it was so much snappier it was hard to believe it was the same motor.

Welding and grinding is all done on the intake, gotta wrinkle black it and get some new pics. Then reassembly time. I had to order a 58 from eBay, thought I had one kicking around the shop but it's eluded me so far.

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